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Morales, Esteban F. E.; Wyrowski, Friedrich; Schuller, Frederic; Menten, Karl M. (2013), ”Stellar clusters in the inner Galaxy and their correlation with cold dust emission”, Astronomy & Astrophysics 560: A76, doi:10.1051/0004-6361/201321626, Bibcode: 2013A&A...560A..76M.
Piskunov, A. E.; Schilbach, E.; Kharchenko, N. V.; Röser, S.; Scholz, R.-D. (January 2008), ”Tidal radii and masses of open clusters”, Astronomy and Astrophysics 477 (1): 165–172, doi:10.1051/0004-6361:20078525, Bibcode: 2008A&A...477..165P.
Park, Byeong-Gon; Sung, Hwankyung; Kang, Yong Hee (December 2001), ”The Galactic Open Cluster NGC 6531 (M21)”, Journal of the Korean Astronomical Society 34 (3): 149–155, doi:10.5303/JKAS.2001.34.3.149, Bibcode: 2001JKAS...34..149P.
Fedele, D.; van den Ancker, M. E.; Henning, Th.; Jayawardhana, R.; Oliveira, J. M. (February 2010), ”Timescale of mass accretion in pre-main-sequence stars”, Astronomy and Astrophysics 510: 7, doi:10.1051/0004-6361/200912810, A72, Bibcode: 2010A&A...510A..72F.
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